A wide variety of electric power supplies have been developed for use with integrated circuits and other devices. Some common examples include DC/DC converters and voltage regulation modules (VRMs). In many applications, including those utilizing low voltage digital circuitry such as microprocessors, the power supply must provide a fast dynamic response to changes or variations in the load or load requirements.
A typical DC/DC converter may convert a DC voltage supplied from one or more power sources to a desired voltage. This can be accomplished using switching devices that selectively couple one or more current sources either to the power supply output or to a return. By dynamically controlling the on/off timing of each switching device, the number of current sources supplying current to the output, and thus the amount of output current supplied to the load, can be dynamically controlled. This is particularly useful when the load current demand varies and the output voltage is desired to remain at a nominal value, or within a range of values.
When the load current demand on the output becomes low, the amount of current switched to the return (referred to as circulating current) typically increases. These circulating currents usually remain active and thus available for dynamic switching from the return to the output in response to an increase in the load current demand.
As recognized by the inventors hereof, one disadvantage of many known power supplies is the amount of power that is consumed or wasted by circulating current. As such, the inventors have identified a need for a power supply having reduced power losses under low load conditions while maintaining a satisfactory dynamic response to changing load requirements.